JP6571389B2 - Nitride semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing the same.

  A nitride semiconductor such as GaN, InGaN, or AlGaN is used as a material of a light emitting diode (LED (Light Emitting Diode)) or a laser diode (LD (Laser Diode)). Nitride semiconductors have a feature that they are excellent in heat resistance or environmental resistance, and are therefore applied to electronic devices.

  On the other hand, bulk crystal growth of nitride semiconductors is difficult. Therefore, the production of a nitride semiconductor substrate having a practical quality is expensive, and thus the nitride semiconductor substrate having a practical quality is very expensive. Therefore, a single crystal sapphire substrate is widely used as a substrate for growing a layer made of a nitride semiconductor single crystal (hereinafter referred to as “nitride semiconductor layer”), and a single method for growing a nitride semiconductor layer is used. A method of epitaxially growing a nitride semiconductor layer (for example, a GaN layer) on a crystalline sapphire substrate by metal organic vapor phase epitaxy (MOVPE) is generally used.

  By the way, when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer, crystal defects or lattice distortions caused by a lattice constant difference between the nitride semiconductor and sapphire are caused. Therefore, the current most common growth method of a nitride semiconductor layer when a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer is a low temperature growth buffer layer made of AlN or GaN at a low temperature of about 600 ° C. Is grown on a single crystal sapphire substrate, and then a desired nitride semiconductor layer is grown on a low-temperature growth buffer layer at a high temperature of 1000 ° C. or higher (for example, Japanese Patent Laid-Open No. 2000-277435 (patent) Reference 1)). By introducing this low-temperature growth buffer layer, the crystal defects are reduced and the lattice distortion is relaxed.

  In nitride semiconductors, bonds between atoms are strong. Therefore, it is generally said that the growth of the nitride semiconductor layer at a high temperature of 1000 ° C. or higher is necessary to improve the crystal quality of the nitride semiconductor layer. The introduction of the low temperature growth buffer layer and the growth of the nitride semiconductor layer at a high temperature of 1000 ° C. or higher enable the nitride semiconductor layer to be epitaxially grown. As a result, LEDs capable of emitting light from ultraviolet rays to green light are widely put into practical use. Has reached.

JP 2000-277435 A JP 2000-58912 A

  However, in recent years, prices of light-emitting elements including nitride semiconductor layers (nitride semiconductor light-emitting elements), particularly general illumination LEDs or backlight blue LEDs, have been rapidly decreasing with the spread of popularization. According to market research, the price level in 2020 is expected to be about 1/5 times the current price level.

  On the other hand, it is expected that the device characteristics (for example, light emission efficiency, light emission intensity, light extraction efficiency, etc.) of the nitride semiconductor light emitting device will be maintained or improved from the current state. In recent years, ultraviolet light emitting devices including nitride semiconductor layers have been greatly expected as small and power-saving new light sources used for sterilization, water purification, various medical fields, high-speed decomposition treatment of pollutants, or resin curing. Yes.

  As described above, it is necessary to reduce the manufacturing cost of the nitride semiconductor light-emitting device while maintaining the device characteristics of the nitride semiconductor light-emitting device or improving the device characteristics. In a single crystal sapphire substrate generally used as a substrate for growing a nitride semiconductor layer, the unit price per area has been decreasing in recent years. However, it is difficult to further reduce the cost of the single crystal sapphire substrate because of the cost of pulling the single crystal sapphire or processing the single crystal sapphire. Incidentally, JP 2000-58912 A (Patent Document 2) proposes forming a hexagonal n-GaN thin film on the Z-plane of a Z-cut quartz substrate.

  The present invention has been made in view of such points, and the object thereof is to maintain or improve the device characteristics compared to the case where a single crystal sapphire substrate is used as a growth substrate for a nitride semiconductor layer. Another object of the present invention is to provide a nitride semiconductor light emitting device at a low cost.

  A first nitride semiconductor light emitting device according to the present invention includes a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, a base layer provided on the substrate, and a nitride provided on the base layer. And a stacked structure including at least one layer made of a semiconductor single crystal. The underlayer includes c-axis oriented crystals and is formed by sputtering.

  A second nitride semiconductor light emitting device according to the present invention includes a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, a base layer provided on the substrate, and a nitride provided on the base layer. And a stacked structure including at least one layer made of a semiconductor single crystal. The underlayer contains c-axis oriented crystals and contains no more than 10 atomic% of noble gas atoms.

The underlayer preferably includes at least one of c-axis aligned AlN crystal, c-axis aligned BN crystal, and c-axis aligned Ga ₂ O ₃ crystal as c-axis aligned crystals. More preferably, the underlayer further contains 10 atom% or less of oxygen atoms apart from the c-axis oriented crystal.

Asperities are preferably formed on the surface of the substrate located on the base layer side.
It is preferable that the substrate further includes first atoms different from silicon atoms and oxygen atoms. The first atoms are preferably included in the substrate so that the refractive index of the substrate is larger than the refractive index of the substrate made of only silicon dioxide. The first atom is preferably at least one of a lanthanum atom and a titanium atom. It is preferable that the substrate contains 1 × 10 ¹⁰ cm ⁻³ or more and 1 × 10 ¹² cm ⁻³ or less of the first atom.

  A p-side electrode is preferably provided on the stacked structure, and an n-side electrode is preferably provided below the base layer instead of the substrate.

  The method for manufacturing a nitride semiconductor light emitting device of the present invention includes a step of forming a base layer containing c-axis oriented crystals on a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component by sputtering, Forming a laminated structure having at least one layer made of a nitride semiconductor single crystal on the base layer.

  It is preferable to further include a step of forming irregularities on the surface of the substrate located on the base layer side. Unevenness may be formed by sandblasting, or unevenness may be formed by wet etching using an etchant containing hydrofluoric acid.

  The method for manufacturing a nitride semiconductor light emitting device of the present invention includes a step of removing a substrate after forming at least one layer made of a nitride semiconductor single crystal, a step of forming a p-side electrode on a laminated structure, It is preferable that the method further includes a step of forming an n-side electrode on the surface of the underlayer exposed by removing.

  According to the present invention, a nitride semiconductor light emitting device whose device characteristics are maintained or higher than the current state can be provided at a lower cost than when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer.

It is sectional drawing of the nitride semiconductor light-emitting device of one Embodiment of this invention. It is sectional drawing of the nitride semiconductor light-emitting device of one Embodiment of this invention. It is sectional drawing which shows 1 process of the manufacturing process of the nitride semiconductor light-emitting device of one Embodiment of this invention. It is sectional drawing of the nitride semiconductor light-emitting device of one Embodiment of this invention.

  As described above, it is required to reduce the manufacturing cost of the nitride semiconductor light-emitting device while maintaining the device characteristics of the nitride semiconductor light-emitting device at the current level or improving them from the current level. However, it is difficult to further reduce the manufacturing cost of the single crystal sapphire substrate. Therefore, as long as a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer, it is difficult to further reduce the manufacturing cost of the nitride semiconductor light emitting device.

  By the way, about silicon dioxide, the growth technique of the large diameter crystal | crystallization by the hydrothermal synthesis method has matured. Further, it is said that a polycrystalline material and an amorphous material can be provided at a lower cost than a single crystal material. Therefore, the present inventors can reduce the manufacturing cost of a nitride semiconductor light emitting device by using a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component as a growth substrate for a nitride semiconductor layer. I thought.

  Here, “single crystal” means that the atomic arrangement direction is exactly the same in any part of the crystal. On the other hand, “polycrystal” means that two or more single crystals are formed in contact with each other in irregular directions. Therefore, two or more plane orientations exist on the surface of the substrate containing polycrystalline silicon dioxide as a main component. “Amorphous” means one having no crystal structure. Therefore, no plane orientation exists on the surface of the substrate containing amorphous silicon dioxide as a main component. For these reasons, when a nitride semiconductor layer is grown on a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component with an underlayer sandwiched, it is difficult to obtain an underlayer with excellent crystal quality. It was considered difficult to obtain a nitride semiconductor layer with excellent quality. Actually, a single crystal substrate is used as a substrate for growing a nitride semiconductor layer. In consideration of the fact that the nitride semiconductor single crystal has a hexagonal crystal structure, a Z-cut quartz substrate or the like may be used as a growth substrate for the nitride semiconductor layer (for example, Patent Document 2).

  In summary, conventionally, in order to grow a nitride semiconductor layer having excellent crystal quality, that is, to improve the device characteristics of the nitride semiconductor light emitting device, an expensive single crystal is used as a growth substrate for the nitride semiconductor layer. I am using the board. Therefore, the present inventors have grown a nitride semiconductor layer having excellent crystal quality even when a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component is used as a growth substrate for the nitride semiconductor layer. We intensively studied possible methods. As a result, a nitride semiconductor layer having excellent crystal quality is grown on the base layer by forming the base layer by a predetermined sputtering method on a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component. I knew that I could do it.

  Based on the above knowledge, the nitride semiconductor light emitting device of the present invention was completed. The present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

  In the following, in order to express the positional relationship, the part described on the lower side of FIGS. 1 to 4 is expressed as “lower”, and the part described on the upper side of FIGS. 1 to 4 is expressed as “upper”. is there. This is an expression for convenience and is different from “upper” and “lower” defined for the direction of gravity.

<< First Embodiment >>
[Structure of nitride semiconductor light emitting device]
FIG. 1 is a cross-sectional view of a nitride semiconductor light emitting device according to a first embodiment of the present invention. The nitride semiconductor light emitting device of this embodiment includes a substrate 100, a base layer 101 provided on the substrate 100, and a stacked structure provided on the base layer 101. The substrate 100 includes polycrystalline silicon dioxide or amorphous silicon dioxide as a main component. The underlayer 101 includes c-axis oriented crystals and is formed by sputtering. Alternatively, the base layer 101 includes c-axis aligned crystals and includes 10 atomic% or less of rare gas atoms. The stacked structure has at least one nitride semiconductor layer (a layer made of a nitride semiconductor single crystal).

  In the present embodiment, a base layer 101, a buffer layer 102, and a stacked structure are sequentially provided on the substrate 100. In the stacked structure, the n-type nitride semiconductor layer 103, the light emitting layer 106, the carrier barrier layer 107, and p. A type nitride semiconductor layer 108 is sequentially provided on the buffer layer 102. The stacked structure is etched so that the n-type nitride semiconductor layer 103 is exposed, and an n-side electrode 110 is provided on the exposed surface of the n-type nitride semiconductor layer 103. A p-side electrode 111 is provided on the p-type nitride semiconductor layer 108.

<Board>
(Polycrystalline silicon dioxide or amorphous silicon dioxide)
The substrate 100 includes polycrystalline silicon dioxide or amorphous silicon dioxide as a main component. Therefore, the manufacturing cost of the substrate 100 can be kept lower than the manufacturing cost of the single crystal silicon dioxide substrate, and thus the manufacturing cost of the substrate 100 can be kept lower than the manufacturing cost of the single crystal sapphire substrate. Therefore, in this embodiment, since the manufacturing cost of the growth substrate for the nitride semiconductor layer can be reduced as compared with the case where the single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer, the manufacture of the nitride semiconductor light emitting device is possible. Cost can be reduced.

  In the present specification, the “substrate including polycrystalline silicon dioxide or amorphous silicon dioxide as a main component” means that the substrate 100 includes 50 mass% or more of polycrystalline silicon dioxide or amorphous silicon dioxide. The substrate 100 preferably contains 70% by mass or more of polycrystalline silicon dioxide or amorphous silicon dioxide, more preferably 90% by mass or more of polycrystalline silicon dioxide or amorphous silicon dioxide.

  In this specification, whether or not the material of the substrate 100 is silicon dioxide is confirmed by Raman spectroscopy. In addition, a measurement sample is manufactured by processing the substrate 100 into a thin film with a FIB (Focused Ion Beam) apparatus, and a TEM (Transmission Electron Microscope) image or a STEM (Scanning Transmission Electron Microscope) image of the manufactured measurement sample is observed. Thus, it is confirmed whether the substrate 100 includes polycrystalline silicon dioxide or amorphous silicon dioxide. In the TEM image or the STEM image, if a weak spot is observed in the electron diffraction pattern, it can be said that polycrystalline silicon dioxide is included in the substrate 100, and a halo pattern is observed in the background of the electron diffraction pattern. In other words, it can be said that the amorphous silicon dioxide is contained in the substrate 100.

  In general, the Raman spectrum reflects the degree of long-range order of the molecular structure. Therefore, the shape of the Raman spectrum is clearly different between single crystal silicon dioxide, polycrystalline silicon dioxide, and amorphous silicon dioxide. Therefore, the shape of the Raman spectrum, the peak intensity of the specific peak appearing in the Raman spectrum, the half-width of the specific peak appearing in the Raman spectrum, the peak position (peak wavelength) of the specific peak appearing in the Raman spectrum, etc. By analyzing, the content of polycrystalline silicon dioxide or amorphous silicon dioxide in the substrate 100 is obtained.

(First atom)
The substrate 100 preferably further includes a first atom that is different from a silicon (Si) atom and an oxygen (O) atom. Here, the first atoms are contained in the substrate 100 to make the refractive index of the substrate 100 larger than the refractive index of the substrate made of only silicon dioxide. That is, the refractive index of the substrate 100 can be increased by adding the first atoms to the substrate 100. Therefore, the light extraction efficiency from the nitride semiconductor light emitting device can be further increased. Here, the “substrate made of only silicon dioxide” means a substrate made of polycrystalline silicon dioxide or amorphous silicon dioxide and further not containing atoms different from Si atoms and O atoms.

  Specifically, GaN, AlN, InN, or the like is known as a nitride semiconductor constituting the nitride semiconductor light emitting device. As for these refractive indexes, the refractive index of GaN is 2.54, the refractive index of AlN is 2.2, and the refractive index of InN is 3.5. The refractive index of these mixed crystals shows a value between the refractive indexes of the nitride semiconductors included in the mixed crystal according to the composition of the mixed crystal. Therefore, in any case, the refractive index difference between the nitride semiconductor and the atmosphere is 1.2 (= 2.2-1) or more, so that the light extraction efficiency from the nitride semiconductor light emitting device is increased. It ’s difficult.

  However, the refractive index of silicon dioxide is about 1.5. Therefore, if the substrate 100 is used as a growth substrate for the nitride semiconductor layer, the difference in refractive index between the nitride semiconductor layer and the substrate 100 becomes 0.7 (= 2.2−1.5) or more, and the substrate 100 and the atmosphere And the refractive index difference is about 0.5 (= 1.5-1). The addition of the first atoms increases the refractive index of the substrate 100, so that the difference in refractive index between the nitride semiconductor layer and the substrate 100 decreases. Thereby, in the surface 100A of the substrate 100 located on the base layer 101 side (hereinafter, “the surface of the substrate located on the base layer side” is referred to as “the upper surface of the substrate”), the reflection of light generated in the light emitting layer 106 is reflected. The rate can be kept low (Snell's law). Therefore, if the substrate 100 contains not only Si atoms and O atoms but also the first atoms, the light extraction efficiency from the nitride semiconductor light emitting device can be increased as compared with a substrate made of only silicon dioxide.

Preferably, the first atom is at least one of a lanthanum (La) atom and a titanium (Ti) atom, and is included in the substrate 100 at 1 × 10 ¹⁰ cm ⁻³ or more and 1 × 10 ¹² cm ⁻³ or less. For example, if the substrate 100 contains not only Si atoms and O atoms but also La atoms in the range of 1 × 10 ¹⁰ cm ^{−3 to} 1 × 10 ¹² cm ⁻³ , the refractive index of the substrate 100 is made of only silicon dioxide. The refractive index is about 0.1 to 0.15 greater than the refractive index. If the substrate 100 contains not only Si atoms and O atoms but also Ti atoms in a range of 1 × 10 ¹⁰ cm ^{−3 to} 1 × 10 ¹² cm ⁻³ , the refractive index of the substrate 100 is that of a substrate made of only silicon dioxide. About 0.03 to 0.05 larger than the rate.

In addition, the present inventors can keep the amount of light generated in the light emitting layer 106 absorbed by the first atoms low when the concentration of the first atoms in the substrate 100 is 1 × 10 ¹² cm ⁻³ or less. It is confirmed that. As a result, the amount of light extracted from the nitride semiconductor light emitting device can be ensured, so that the light extraction efficiency from the nitride semiconductor light emitting device can be maintained high. More preferably, the substrate 100 includes a first atom of 1 × 10 ¹⁰ cm ^{−3 to} 5 × 10 ¹¹ cm ⁻³ .

  In this specification, the type and concentration of the first atom contained in the substrate 100 are obtained by WD-TXRF (Wavelength-Dispersive Total reflection X-Ray Fluorescence). The position of the first atom in the substrate 100 is not particularly limited. When the substrate 100 includes polycrystalline silicon dioxide as a main component, the first atoms may be provided between adjacent single crystal silicon dioxides or may be scattered in the substrate 100. When the substrate 100 includes amorphous silicon dioxide as a main component, the first atoms are preferably scattered in the substrate 100.

  Although the substrate 100 has been described above, since the substrate 100 contains polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, it exhibits high transmittance not only for visible light but also for ultraviolet rays and deep ultraviolet rays. “Visible light” means an electromagnetic wave having a wavelength of 360 nm or more and 830 nm or less, “ultraviolet light” means an electromagnetic wave having a wavelength of more than 320 nm and less than 360 nm, and “deep ultraviolet” means that the wavelength is The electromagnetic wave which is 200 nm or more and 320 nm or less is meant. Therefore, an ultraviolet light emitting element or a deep ultraviolet light emitting element can be provided using the substrate 100. Also from this, the substrate 100 can be used as an alternative to the single crystal sapphire substrate. The thickness of the substrate 100 is preferably 200 μm or more and 1500 μm or less.

<Underlayer>
As described above, the base layer 101 is formed by sputtering. Therefore, even when the substrate 100 is used as a growth substrate for a nitride semiconductor layer, a nitride semiconductor layer having excellent crystal quality can be grown on the base layer 101. The reason why such an effect can be obtained is considered as follows.

  In the sputtering method, electrons or ions generated by ionization of an inert gas collide with the target at high speed, and heavy atoms or molecules constituting the target are knocked out of the target (sputtering phenomenon). The heavy atoms or molecules ionized by the sputtering phenomenon arrive at the film formation surface (in this embodiment, the upper surface 100A of the substrate 100) with a large kinetic energy and adhere to the film formation surface. In this way, a film is formed on the film formation surface.

  As described above, the “sputtering method” is a method of physically forming a film on the film formation surface without causing a chemical reaction or a phase change. Therefore, there is no selectivity of the substrate 100. That is, a substrate that cannot be used when a film is chemically formed (for example, a film is formed by a chemical vapor deposition (CVD) method) can be used as a substrate for growing a nitride semiconductor layer. Therefore, even when the substrate 100 is used as a growth substrate for a nitride semiconductor layer, the base layer 101 can be formed without inheriting the crystal quality of the substrate 100 or the like.

  Further, in the sputtering method, the film is physically formed on the film formation surface, so that the film can be formed while maintaining the properties inherent to the target material. In addition, even when a material having a high melting point is used as the target material, film formation can be performed while the composition of the target material is maintained. For example, a material having an ionic bond has a property that it is easily c-axis oriented and has a high melting point. Therefore, if a target made of a material having an ionic bond is used as a target for forming the base layer 101, the base layer 101 is formed while maintaining the property of being easily c-axis oriented and the composition of the target material. it can. Accordingly, the formed underlayer 101 includes c-axis oriented crystals and crystals made of the composition of the target material. Therefore, the base layer 101 having excellent crystal quality can be formed. In addition, since the target made of a material having an ionic bond is obtained at a low cost, the base layer 101 can be provided at a low cost. In the sputtering method, since the film is physically formed on the film formation surface, it is not necessary to set or change the film formation conditions in consideration of the progress of the chemical reaction. From the above, the base layer 101 having excellent crystal quality can be easily formed at low cost.

  Further, in the sputtering method, ionized heavy atoms or molecules arrive at the film formation surface with a large kinetic energy, and thus adhere to the film formation surface with a strong adhesion force. Therefore, since at least a part of the formed base layer 101 can be prevented from peeling from the upper surface 100A of the substrate 100, the base layer 101 can be formed without forming a through hole (for example, a micropipe-like through hole). .

  Thus, even when the substrate 100 is used as a growth substrate for a nitride semiconductor layer, the base layer 101 is formed on the upper surface 100A of the substrate 100 by sputtering using a target made of a material having ionic bonds. For example, the base layer 101 having excellent crystal quality can be formed on the upper surface 100A of the substrate 100 at low cost without forming through holes. Thereby, the upper surface 100A of the substrate 100 is covered with the underlayer 101 having excellent crystal quality. Therefore, since the nitride semiconductor layer can be formed on the base layer 101 without inheriting the crystal quality of the substrate 100, a nitride semiconductor layer having excellent crystal quality can be formed. Therefore, it is possible to provide a nitride semiconductor light emitting device whose device characteristics are maintained or higher than the current state at a lower cost than when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer.

Examples of the material having an ionic bond include AlN, BN, and Ga ₂ O ₃ . Therefore, the base layer 101 includes at least one of a c-axis aligned AlN crystal, a c-axis aligned BN crystal, and a c-axis aligned Ga ₂ O ₃ crystal as the c-axis aligned crystal. Is preferred. By measuring the X-ray diffraction spectrum of the underlayer 101, the c-axis oriented crystal material can be confirmed.

More preferably, the base layer 101 further includes 10 atom% or less of oxygen atoms apart from the c-axis oriented crystal. Thereby, the c-axis orientation of a crystal (for example, AlN crystal, BN crystal, or Ga ₂ O ₃ crystal) included in the base layer 101 can be maintained high. Therefore, it is possible to provide a nitride semiconductor light-emitting device with further improved device characteristics at a lower cost than when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer. More preferably, the base layer 101 further includes oxygen atoms of 3 atom% or more and 8 atom% or less separately from the c-axis oriented crystal. In this specification, “the underlayer further contains 10 atomic% or less oxygen atoms apart from c-axis oriented crystals” does not constitute a crystal structure of crystals in which such oxygen atoms are c-axis oriented. Means that. In this specification, the concentration of the oxygen atom in the underlayer 101 is obtained by SIMS (Secondary Ion Mass Spectrometry).

  As described above, by forming the base layer 101 by sputtering using a target made of a material having an ionic bond, the base layer includes c-axis oriented crystals and crystals made of the composition of the target material. 101 can be formed. Therefore, in this specification, “the base layer includes a c-axis oriented crystal” means that the base layer 101 is formed by a sputtering method using a target made of a material having an ionic bond. .

  The “c-axis oriented crystal” means that the crystal is integrated so that the c-plane ((001) plane) of the crystal is parallel to the upper surface 100A of the substrate 100. If the half-value width of the X-ray rocking curve of the surface (0002) of the underlayer 101 is 1000 seconds or less and the half-value width of the X-ray rocking curve of the surface (1-102) of the underlayer 101 is 1000 seconds or less It can be said that the crystals contained in the underlayer 101 are c-axis oriented.

  Furthermore, as described above, in the sputtering method, since the film forming process is performed in an atmosphere of an inert gas, it is said that the film is formed by taking in the inert gas. Therefore, in this specification, “the underlayer is formed by a sputtering method” can be rephrased as “the underlayer contains no more than 10 atomic% of noble gas atoms”. In other words, it includes 3 to 8 atomic% of noble gas atoms. In this specification, the concentration of rare gas atoms in the base layer 101 is obtained by SIMS. In general, a rare gas such as argon (Ar), krypton (Kr), or xenon (Xe) is used as the inert gas.

  The base layer 101 has been described above, but the thickness of the base layer 101 is preferably 500 nm or more. As a result, the upper surface 100A of the substrate 100 is completely covered with the base layer 101, so that the crystal quality of the nitride semiconductor layer formed on the base layer 101 can be further improved. More preferably, the thickness of the base layer 101 is not less than 500 nm and not more than 2000 nm.

<Buffer layer>
By providing the buffer layer 102 between the base layer 101 and the stacked structure, the crystal quality of the nitride semiconductor layer included in the stacked structure can be further improved. Thereby, the device characteristics of the nitride semiconductor light emitting device can be further improved. Therefore, it is possible to provide a nitride semiconductor light-emitting device with further improved device characteristics at a lower cost than when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer.

  The buffer layer 102 may be made of AlGaN, but is preferably made of AlN. If the buffer layer 102 is made of AlN, it is possible to prevent the occurrence of cracks due to lattice mismatch between the material of the base layer 101 and the material of the nitride semiconductor layer included in the stacked structure. Specifically, the buffer layer 102 applies a compressive stress to the base layer 101 regardless of the composition of the nitride semiconductor constituting the nitride semiconductor layer included in the stacked structure. . Therefore, the occurrence of the crack can be prevented.

  The thickness of the buffer layer 102 is preferably 2 μm or more and 6 μm or less. Thereby, the crystal quality of the nitride semiconductor layer included in the stacked structure can be further enhanced. In particular, if the thickness of the buffer layer 102 is 6 μm or less, the buffer layer 102 can be prevented from adversely affecting the crystal quality of the nitride semiconductor layer.

<Laminated structure>
(N-type nitride semiconductor layer)
The nitride semiconductor constituting the n-type nitride semiconductor layer 103 is preferably GaN, AlGaN, InGaN or InAlGaN, and may be a mixed crystal composed of at least two of these. It is preferable that the composition of the nitride semiconductor constituting the n-type nitride semiconductor layer 103 is determined in accordance with the emission wavelength required for the nitride semiconductor light emitting device. Thereby, the light generated in the light emitting layer 106 can be prevented from being absorbed by the n-type nitride semiconductor layer 103. Therefore, since the amount of light extracted from the nitride semiconductor light emitting device can be secured, the light extraction efficiency from the nitride semiconductor light emitting device can be maintained high.

For example, if the nitride semiconductor constituting the n-type nitride semiconductor layer 103 is Al _x1 Ga _1-x1 N (0.7 ≦ x1 ≦ 1), light (for example, deep ultraviolet light) generated in the light emitting layer 106 is n It can be prevented from being absorbed by the type nitride semiconductor layer 103. Further, if the nitride semiconductor constituting the n-type nitride semiconductor layer 103 is Al _x2 Ga _1-x2 N (0.5 ≦ x2 ≦ 1), light (for example, ultraviolet rays) generated in the light emitting layer 106 is n-type. The absorption by the nitride semiconductor layer 103 can be prevented. Further, if the nitride semiconductor constituting the n-type nitride semiconductor layer 103 is In _x3 Ga _1-x3 N (0 ≦ x3 ≦ 0.05), light (for example, visible light) generated in the light emitting layer 106 is n. It can be prevented from being absorbed by the type nitride semiconductor layer 103.

The concentration of the n-type impurity in the n-type nitride semiconductor layer 103 is preferably 1 × 10 ¹⁶ cm ⁻³ or more and 8 × 10 ¹⁸ cm ⁻³ or less, more preferably 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 or less. ¹⁸ cm ⁻³ or less. It is preferable that the concentration of the n-type impurity in the n-type nitride semiconductor layer 103 is determined in accordance with element characteristics required for the nitride semiconductor light emitting element. The n-type impurity may be at least one of Si, Se, and Ge, but is preferably Si.

  The thickness of the n-type nitride semiconductor layer 103 is preferably 1 μm or more and 4 μm or less. The n-type nitride semiconductor layer 103 may be formed by stacking two or more layers having at least one of the composition of the nitride semiconductor, the concentration and the thickness of the n-type impurity, different from each other. .

(Light emitting layer)
The light emitting layer 106 is preferably a structure in which the well layer 105 is sandwiched between the barrier layers 104. The composition of the nitride semiconductor constituting the barrier layer 104, the thickness of the barrier layer 104, the composition of the nitride semiconductor constituting the well layer 105, depending on the emission wavelength or device characteristics required for the nitride semiconductor light emitting device, Alternatively, the thickness of the well layer 105 is preferably determined. The thickness of the barrier layer 104 and the thickness of the well layer 105 are preferably determined in consideration of the formation of quantum levels in the light emitting layer 106.

For example, in a nitride semiconductor light emitting device that generates deep ultraviolet rays, the well layer 105 preferably contains Al, and more preferably consists of Al _s1 Ga _{1 -s1} N (0.4 ≦ s1 ≦ 0.6). In the nitride semiconductor light emitting device that generates ultraviolet rays, the well layer 105 preferably contains Al, more preferably Al _s2 Ga _{1 -s2} N (0.05 ≦ s2 ≦ 0.3). In the nitride semiconductor light emitting device that generates visible light, the well layer 105 preferably contains In, and more preferably consists of In _s3 Ga _{1 -s3} N (0.08 ≦ s3 ≦ 0.7).

The barrier layer 104 preferably has a larger band gap energy than the well layer 105 and preferably does not absorb light generated in the light emitting layer 106. For example, in a nitride semiconductor light emitting device that generates deep ultraviolet light, the Al composition of the nitride semiconductor constituting the barrier layer 104 is preferably higher than the Al composition of the nitride semiconductor constituting the well layer 105. For example, the barrier layer 104 is preferably made of Al _t1 Ga _1-t1 N (0.45 ≦ t1 ≦ 0.65). As described above, in the nitride semiconductor light emitting device that generates deep ultraviolet rays, the Al composition of the nitride semiconductor constituting each of the barrier layer 104 and the well layer 105 is increased, so that holes (holes have a large effective mass). Is difficult to be injected from the p-type nitride semiconductor layer 108 into the light emitting layer 106 (particularly, the well layer 105). Therefore, when the thickness of the barrier layer 104 is increased, holes are not easily injected into the well layer 105. In addition, when the thickness of the well layer 105 is increased, it becomes difficult to inject holes into the well layer 105 located in the center of the light emitting layer 106 in the thickness direction. From the above, the thickness of the barrier layer 104 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less. Further, the thickness of the well layer 105 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less.

In the nitride semiconductor light emitting device that generates ultraviolet light, the Al composition of the nitride semiconductor constituting the barrier layer 104 is preferably higher than the Al composition of the nitride semiconductor constituting the well layer 105. For example, the barrier layer 104 is preferably made of Al _t2 Ga _{1 -t2} N (0.08 ≦ t2 ≦ 0.35). In this case, the thickness of the barrier layer 104 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less. Further, the thickness of the well layer 105 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less.

In the nitride semiconductor light emitting element that generates visible light, the In composition of the nitride semiconductor that forms the barrier layer 104 is preferably lower than the In composition of the nitride semiconductor that forms the well layer 105. For example, the barrier layer 104 is preferably made of In _t3 Ga _{1 -t3} N (0.05 ≦ t3 ≦ 0.65). In this case, the thickness of the barrier layer 104 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less. Further, the thickness of the well layer 105 is preferably 5 nm or less, more preferably 1 nm or more and 5 nm or less.

  The number of barrier layers 104 in the light-emitting layer 106 is not limited as long as the hole injection efficiency from the p-type nitride semiconductor layer 108 to the light-emitting layer 106 (particularly, the well layer 105) can be maintained high. The number of well layers 105 in FIG.

(Carrier barrier layer)
The carrier barrier layer 107 means a layer having a function of preventing electrons injected into the light emitting layer 106 from overflowing to the p-type nitride semiconductor layer 108 side. Therefore, the Al composition of the nitride semiconductor that constitutes the carrier barrier layer 107 is preferably higher than the Al composition of the nitride semiconductor that constitutes each of the barrier layer 104 and the well layer 105. In addition, the carrier barrier layer 107 preferably has a thickness equal to or greater than the minimum thickness that can exhibit the above functions.

On the other hand, when the thickness of the layer having a high Al composition in the nitride semiconductor is increased, the series resistance of the nitride semiconductor light emitting device is increased, and thus the power conversion efficiency of the nitride semiconductor light emitting device is lowered. In addition, if the thickness of the carrier barrier layer 107 is large, holes are hardly injected from the p-type nitride semiconductor layer 108 into the light emitting layer 106 (particularly, the well layer 105). Based on the above, it is preferable to determine the composition of the nitride semiconductor composing the carrier barrier layer 107 and the thickness of the carrier barrier layer 107. For example, the carrier barrier layer 107 is preferably made of Al _u1 Ga _1-u1 N (0.7 ≦ u1 ≦ 0.9), more preferably Al _u1 Ga _1-u1 N (0.75 ≦ u1 ≦ 0. 9). The thickness of the carrier barrier layer 107 is preferably 10 nm or more and 200 nm or less, and more preferably 30 nm or more and 200 nm or less.

  Note that the carrier barrier layer 107 preferably contains a p-type impurity. As a result, the series resistance of the nitride semiconductor light emitting device can be kept low. Mg can be used as the p-type impurity.

(P-type nitride semiconductor layer)
The same applies to the nitride semiconductor constituting the p-type nitride semiconductor layer 108 as the nitride semiconductor constituting the n-type nitride semiconductor layer 103. For example, if the nitride semiconductor constituting the p-type nitride semiconductor layer 108 is Al _y1 Ga _{1 -y1} N (0.7 ≦ y1 ≦ 1), the light (for example, deep ultraviolet light) generated in the light emitting layer 106 is p. Absorption by the type nitride semiconductor layer 108 can be prevented. If the nitride semiconductor composing the p-type nitride semiconductor layer 108 is Al _y2 Ga _{1 -y2} N (0.5 ≦ y2 ≦ 1), the light (for example, ultraviolet rays) generated in the light emitting layer 106 is p-type. The absorption by the nitride semiconductor layer 108 can be prevented. Further, if the nitride semiconductor constituting the p-type nitride semiconductor layer 108 is In _y3 Ga _{1 -y3} N (0 ≦ y3 ≦ 0.05), the light (for example, visible light) generated in the light emitting layer 106 is p. Absorption by the type nitride semiconductor layer 108 can be prevented.

The concentration of the p-type impurity in the p-type nitride semiconductor layer 108 is preferably 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²⁰ cm ⁻³ or less. It is preferable that the concentration of the p-type impurity in the p-type nitride semiconductor layer 108 is determined in accordance with element characteristics required for the nitride semiconductor light-emitting element. For example, if the p-type impurity concentration in the p-type nitride semiconductor layer 108 is high, the series resistance of the nitride semiconductor light-emitting element can be kept low.

  The thickness of such p-type nitride semiconductor layer 108 is preferably 0.05 μm or more and 1.5 μm or less, and more preferably 0.5 μm or more and 1.5 μm or less. The p-type nitride semiconductor layer 108 is provided on the first p-type nitride semiconductor layer provided on the carrier barrier layer 107 and the first p-type nitride semiconductor layer, and the concentration of the p-type impurity. It is preferable to have a second p-type nitride semiconductor layer higher than the first p-type nitride semiconductor layer. Thereby, the series resistance of the nitride semiconductor light emitting element can be further reduced.

<N-side electrode, p-side electrode>
As a material of the n-side electrode 110, a general material can be used without particular limitation as a material of a contact electrode for the n-type nitride semiconductor layer. For example, Ni / Au can be used. As a material of the p-side electrode 111, a general material can be used without particular limitation as a material of a contact electrode for the p-type nitride semiconductor layer. For example, Pd / Au can be used.

  As the thickness of the n-side electrode 110, a general thickness as a thickness of the contact electrode for the n-type nitride semiconductor layer can be adopted without particular limitation, but is preferably 1 μm or more. Thereby, wire bonding can be performed on the n-side electrode 110. The same can be said for the thickness of the p-side electrode 111.

[Manufacture of nitride semiconductor light emitting devices]
In the nitride semiconductor light emitting device manufacturing method shown below, the nitride semiconductor light emitting device of this embodiment is obtained by dividing a nitride semiconductor light emitting device forming wafer (hereinafter simply referred to as “wafer”) into chips. Yes. In the following description, a method for manufacturing a nitride semiconductor light-emitting device will be described by attaching the reference numerals of the corresponding components of the nitride semiconductor light-emitting device to the components of the wafer. The material and thickness of the constituent elements of the wafer are as described in the above [Structure of nitride semiconductor light emitting device].

<Formation of underlayer>
In the formation process of the base layer 101, the base layer 101 including c-axis oriented crystals is formed on the substrate 100 by a sputtering method.

  For example, first, the substrate 100 is set at a predetermined position in the sputtering apparatus, and the target is set at a predetermined position in the sputtering apparatus. At this time, the substrate 100 is placed in the sputtering apparatus so that the upper surface 100A of the substrate 100 faces the target.

  As the substrate 100 installed in the sputtering apparatus, a substrate 100 having a diameter of 2 inches (50.8 mm) or more is preferably used, and a substrate 100 having a diameter of 4 inches (101.6 mm) or more is preferably used. More preferred. The substrate 100 having a diameter of 4 inches or more can be kept at a lower price per unit area than the substrate 100 having a diameter of 2 inches or more. Therefore, if the substrate 100 having a diameter of 4 inches (101.6 mm) or more is used, the manufacturing cost of the nitride semiconductor light emitting device can be further reduced.

  As the substrate 100 installed in the sputtering apparatus, it is preferable to use the substrate 100 that has been cleaned with an organic solvent and then cleaned with pure water. By performing the washing twice, organic substances or particulate deposits can be removed from the surface of the substrate 100. Therefore, the substrate 100 on which the organic substance or the fine particle deposit or the like is not attached to the surface can be used as the growth substrate for the nitride semiconductor layer. Here, as an organic solvent, the organic solvent generally used as a solvent for washing | cleaning can be used.

  As a target installed in the sputtering apparatus, a target made of a single crystal material may be used, but a target made of a polycrystalline material is preferably used. Thereby, since the formation cost of the foundation | substrate layer 101 can be restrained low, the manufacturing cost of a nitride semiconductor light-emitting device can be restrained low.

  As the sputtering apparatus, a sputtering apparatus generally used for manufacturing a nitride semiconductor light emitting element can be used without any particular limitation.

  Next, after evacuating the sputtering apparatus, an inert gas is introduced into the sputtering apparatus, and a high-frequency voltage is applied between the substrate 100 and the target. As a result, high-frequency discharge occurs in the sputtering apparatus, so that a sputtering phenomenon occurs. Therefore, the base layer 101 is formed on the upper surface 100A of the substrate 100 by sputtering.

  When the base layer 101 is formed, it is not necessary to heat the substrate 100, but it is preferable to heat the substrate 100. Heating the substrate 100 during the formation of the underlayer 101 facilitates c-axis orientation of crystals contained in the underlayer 101, so that the underlayer 101 having excellent crystal quality is easily formed. In order to effectively obtain such an effect, the heating temperature of the substrate 100 is preferably set to 400 ° C. or lower, and the heating temperature of the substrate 100 is more preferably set to 50 ° C. or higher and 150 ° C. or lower. If the heating temperature of the substrate 100 is 400 ° C. or lower, an effect that nitrogen atoms can be prevented from dissociating from the target when the target material contains nitrogen atoms (for example, when the target is made of AlN) is also obtained.

<Formation of buffer layer>
In the formation process of the buffer layer 102, the buffer layer 102 is formed on the base layer 101 by, for example, the MOCVD (Metal Organic Chemical Vapor Deposition) method. This contributes to mass production of the buffer layer 102, and thus contributes to mass production of the nitride semiconductor light emitting device.

  For example, first, the substrate 100 on which the base layer 101 is formed is taken out of the sputtering apparatus and placed in the MOCVD apparatus. As the MOCVD apparatus, a MOCVD apparatus generally used for manufacturing a nitride semiconductor light emitting element can be used without any particular limitation.

  Next, the temperature of the substrate 100 is raised. At this time, it is preferable to raise the temperature of the substrate 100 in an atmosphere containing at least one of hydrogen, ammonia, and nitrogen. When the base layer 101 contains nitrogen atoms (for example, when the base layer 101 contains c-axis oriented AlN crystal), it is preferable to raise the temperature of the substrate 100 in an atmosphere containing ammonia. Thereby, even when the temperature of the substrate 100 exceeds 400 ° C., dissociation of nitrogen atoms from the base layer 101 can be prevented.

  Subsequently, the growth of the nitride semiconductor single crystal is started while the temperature of the substrate 100 is maintained. In the case of manufacturing a nitride semiconductor light emitting device that generates deep ultraviolet rays, a nitride semiconductor single crystal containing Al is often grown. Therefore, it is preferable to grow the nitride semiconductor single crystal while maintaining the temperature of the substrate 100 at 1000 ° C. or higher. In the case of manufacturing a nitride semiconductor light emitting device that generates ultraviolet rays, a nitride semiconductor single crystal containing Al is often grown. Therefore, it is preferable to grow the nitride semiconductor single crystal while maintaining the temperature of the substrate 100 at a temperature of 1200 ° C. or higher. In the case of manufacturing a nitride semiconductor light emitting element that generates visible light, a nitride semiconductor single crystal containing In is often grown. Therefore, it is preferable to grow the nitride semiconductor single crystal while keeping the temperature of the substrate 100 at a temperature of 700 ° C. or lower.

<Formation of laminated structure>
In the formation process of the stacked structure, the n-type nitride semiconductor layer 103, the light emitting layer 106, the carrier barrier layer 107, and the p-type nitride semiconductor layer 108 are sequentially formed on the buffer layer 102. It is preferable to form a laminated structure by MOCVD. At this time, a stacked structure may be formed using the MOCVD apparatus used to form the buffer layer 102, or a stacked structure using a MOCVD apparatus different from the MOCVD apparatus used to form the buffer layer 102. May be formed. In this way, a wafer is manufactured.

<Formation of n-side electrode and p-side electrode>
In the formation process of the n-side electrode 110 and the p-side electrode 111, the n-side electrode 110 is formed on the exposed surface of the n-type nitride semiconductor layer 103, and the p-side electrode 111 is formed on the upper surface of the p-type nitride semiconductor layer 108. .

  For example, first, after removing the wafer from the MOCVD apparatus, p-type impurities are activated. Thereafter, the p-type nitride semiconductor layer 108, the carrier barrier layer 107, the light emitting layer 106, and the n-type nitride semiconductor layer 103 are etched by photolithography and RIE (Reactive Ion Etching) to expose the n-type nitride semiconductor layer 103. Form a surface. For example, the n-side electrode 110 is formed on the exposed surface of the n-type nitride semiconductor layer 103 by vacuum evaporation.

  Further, a mask is formed in a region different from the formation region of the p-side electrode 111 on the upper surface of the p-type nitride semiconductor layer 108 by, for example, photolithography. Thereafter, the p-side electrode 111 is formed on a portion of the upper surface of the p-type nitride semiconductor layer 108 exposed from the mask, for example, by vacuum deposition.

  Heat treatment is preferably performed after the n-side electrode 110 and the p-side electrode 111 are formed. Thereby, the n-side electrode 110 is sintered, so that the n-side electrode 110 and the n-type nitride semiconductor layer 103 are in ohmic contact. Further, the p-side electrode 111 is sintered, so that the p-side electrode 111 and the p-type nitride semiconductor layer 108 are in ohmic contact.

<Individualization>
For example, the wafer is divided into chips by dicing or laser scribing. In this way, a nitride semiconductor light emitting device is manufactured. Preferably, the manufactured nitride semiconductor light emitting element is mounted on a stem, and after the nitride semiconductor light emitting element and the stem are electrically connected, the nitride semiconductor light emitting element is sealed with a resin or the like.

<< Second Embodiment >>
FIG. 2 is a cross-sectional view of the nitride semiconductor light emitting device according to the second embodiment of the present invention. The nitride semiconductor light emitting device of this embodiment includes a substrate 200 having an uneven surface 210 formed on the upper surface, instead of the substrate 100 of the first embodiment. In the following, differences from the first embodiment will be mainly described.

  In this embodiment, since the unevenness 210 is formed on the upper surface of the substrate 200, the light generated in the light emitting layer 106 is scattered on the upper surface of the substrate 200. As a result, light incident on the surface of the unevenness 210 at a predetermined incident angle (0 ° <incident angle <90 °) (light generated in the light emitting layer 106) is also taken out of the nitride semiconductor light emitting device. Therefore, the light extraction efficiency from the nitride semiconductor light emitting device can be further increased.

  When the base layer 101 is chemically formed on the upper surface of the substrate 200, the progress of the chemical reaction or the flow of the reactive gas is uneven on the upper surface of the substrate 200 due to the unevenness 210. Therefore, it is difficult to perform the film formation process uniformly on the upper surface of the substrate 200, and the film formation process is affected by the flatness of the upper surface of the substrate 200.

  However, in the present embodiment, as in the first embodiment, since the base layer 101 is formed on the upper surface of the substrate 200 by sputtering, it is physically formed on the upper surface of the substrate 200. is there. Therefore, the base layer 101 can be formed without being affected by the progress of the chemical reaction or the flow of the reactive gas. Therefore, even when the unevenness 210 is formed on the upper surface of the substrate 200, the base layer 101 having a uniform crystal quality can be formed on the upper surface of the substrate 200. A nitride semiconductor layer with uniform quality can be formed. Therefore, the light extraction efficiency of the nitride semiconductor light emitting device can be improved by forming the unevenness 210 on the upper surface of the substrate 200. As described above, it is possible to provide a nitride semiconductor light emitting device with further improved device characteristics (for example, light extraction efficiency) compared to the case where a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer.

  In the unevenness 210, the shape of the recess or protrusion, the size of the recess or protrusion, the number of the recess or protrusion, the interval between the recesses or protrusions, and the like are not particularly limited. Moreover, in the adjacent recessed part, the shape or magnitude | size of a recessed part may mutually be the same, or may mutually differ. This is also true for adjacent convex portions. Further, the interval between the recesses on the upper surface of the substrate 200 may be uniform or different from each other. This is also true for the interval between the protrusions on the upper surface of the substrate 200. For example, the shape of the concave portion or the convex portion is preferably a cone or a polygonal pyramid, the depth of the concave portion or the height of the convex portion is preferably 50 nm or more and 500 nm or less, and the interval between adjacent concave portions or adjacent convex portions Is preferably 50 μm or more and 200 μm or less.

  The formation method of the unevenness | corrugation 210 is not specifically limited. When uneven processing is performed on a single crystal sapphire substrate, it is necessary to irradiate the single crystal sapphire substrate with high-power excimer laser light or the like. For this reason, it is difficult to perform uneven processing on the single crystal sapphire substrate. However, since the substrate 200 contains polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, the substrate 200 is processed to be uneven by sand blasting or wet etching using an etchant containing hydrofluoric acid. Can do. Therefore, it is possible to perform the uneven processing on the substrate 200 more easily and at a lower cost than the uneven processing on the single crystal sapphire substrate. Therefore, it is possible to provide a nitride semiconductor light emitting device with further improved device characteristics (for example, light extraction efficiency) compared to the case where a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer.

  As conditions for sandblasting, general conditions can be used without particular limitation as conditions for sandblasting when forming irregularities on the surface of the substrate. If the size of the abrasive particles used in sandblasting or the time during which the abrasive particles are sprayed onto the upper surface of the substrate 200 is changed, the shape or size of the unevenness 210 is changed.

  Moreover, as conditions for wet etching using an etchant containing hydrofluoric acid, general conditions can be used without particular limitation as conditions for wet etching when forming irregularities on the surface of the substrate. If the time for immersing the upper surface of the substrate 200 in the etchant is changed, the shape or size of the unevenness 210 is changed.

<< Third Embodiment >>
FIG. 3 is a cross-sectional view showing one step of the manufacturing process of the nitride semiconductor light emitting device of the third embodiment of the present invention. FIG. 4 is a cross-sectional view of the nitride semiconductor light emitting device of this embodiment. In this embodiment, the substrate 100 is removed after the stacked structure is formed. Therefore, the manufactured nitride semiconductor light emitting device does not include the substrate 100 (FIG. 4). In the following, differences from the first embodiment will be mainly described.

[Manufacture of nitride semiconductor light emitting devices]
<Formation of laminated structure and p-side electrode>
First, after forming a wafer according to the method described in the first embodiment, the p-type impurity is activated. The p-side electrode 311 is formed on the upper surface of the p-type nitride semiconductor layer 108 according to the method described in the first embodiment without etching the stacked structure or the like. Thereafter, the support base 312 is bonded to the upper surface of the p-side electrode 311. In this way, the laminate shown in FIG. 3 is formed.

  The support base 312 preferably has conductivity. Thereby, the electrical resistance generated when a voltage is applied to the nitride semiconductor light emitting element can be suppressed to a low level.

  More preferably, the support base 312 is made of a material having a thermal expansion coefficient comparable to that of the nitride semiconductor constituting the nitride semiconductor layer included in the stacked structure. Thereby, the generation of cracks due to the difference in thermal expansion coefficient between the material of the support base 312 and the material of the nitride semiconductor layer included in the laminated structure can be prevented. An example of such a material is tungsten.

  The adhesive for bonding the support base 312 to the upper surface of the p-side electrode 311 preferably has conductivity. Also by this, the electric resistance generated when a voltage is applied to the nitride semiconductor light emitting element can be suppressed low. Such an adhesive is preferably an adhesive generally used when an integrated circuit is bonded to a mounting substrate or the like (for example, an adhesive having a thermosetting property), but has a low melting point. An adhesive (for example, solder) may be used.

<Removal of substrate>
Next, the laminate shown in FIG. 3 is immersed in an etchant containing hydrofluoric acid. Thereby, the substrate 100 is selectively removed. Depending on the size of the substrate 100, it is preferable to change the time for immersing the laminate shown in FIG. 3 in the etchant.

<Formation of n-side electrode>
Subsequently, the surface of the base layer 101 exposed by removing the substrate 100 (also referred to as “the surface of the base layer 101 located on the side opposite to the stacked structure”) is hereinafter referred to as “exposed surface of the base layer”. ) An n-side electrode 310 is formed on 101A. At this time, the n-side electrode 310 is preferably formed in a stripe pattern on the exposed surface 101A of the base layer 101, and more preferably, the n-side electrode 310 is formed in a matrix pattern on the exposed surface 101A of the base layer 101. Thus, the nitride semiconductor light emitting device of this embodiment is manufactured (FIG. 4).

[Configuration of nitride semiconductor light emitting device]
In the nitride semiconductor light emitting device manufactured in this way, as shown in FIG. 4, the underlayer 101, the buffer layer 102, the n-type nitride semiconductor layer 103, the light emitting layer 106, the carrier barrier layer 107, and the p-type nitride are formed. The semiconductor layer 108 is provided in this order. The n-side electrode 310 is provided in a stripe shape or a matrix shape on the exposed surface 101 A of the base layer 101, and the p-side electrode 311 is provided on the lower surface of the p-type nitride semiconductor layer 108.

  In the nitride semiconductor light emitting device of this embodiment, the n-side electrode 310 is provided on the upper surface side of the device, and the p-side electrode 311 is provided on the lower surface side of the device. As a result, in the nitride semiconductor light emitting device of this embodiment, the current flowing between the n-side electrode 310 and the p-side electrode 311 flows perpendicularly to the light emitting layer 106. That is, the nitride semiconductor light emitting device of this embodiment is a so-called vertical structure nitride semiconductor light emitting device.

  Here, the nitride semiconductor light emitting device includes a vertical structure nitride semiconductor light emitting device and a lateral structure nitride semiconductor light emitting device. In the nitride semiconductor light emitting device having a lateral structure, a current flowing between the n-side electrode and the p-side electrode flows in parallel to the light emitting layer (see FIG. 1 or FIG. 2). Therefore, in the nitride semiconductor light emitting device having the lateral structure, the light emission area in the light emitting layer 106 is smaller than that in the nitride semiconductor light emitting device having the vertical structure, and thus the amount of light extracted per unit size of the nitride semiconductor light emitting device is reduced. Decreases. In addition, the electrical resistance generated when current flows inside the nitride semiconductor light emitting device increases. Therefore, if the device structure of the vertical structure nitride semiconductor light emitting device is exactly the same as that of the lateral structure nitride semiconductor light emitting device, the vertical structure nitride semiconductor light emitting device emits the lateral structure nitride semiconductor light emitting device. Element characteristics superior to those of the elements will be exhibited. From the above, it is said that it is preferable to provide a nitride semiconductor light emitting device having a vertical structure rather than a nitride semiconductor light emitting device having a horizontal structure.

  However, in order to manufacture a nitride semiconductor light emitting device having a vertical structure, it is necessary to remove the growth substrate of the nitride semiconductor layer in the manufacturing process. When a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer, the single crystal sapphire substrate is removed by irradiating the single crystal sapphire substrate with a high-power excimer laser beam or the like. Therefore, it is difficult to remove the growth substrate for the nitride semiconductor layer, so that it is difficult to provide a nitride semiconductor light emitting element having a vertical structure at low cost.

  On the other hand, when the substrate 100 is used as a growth substrate for the nitride semiconductor layer, the substrate 100 can be removed by immersing the stacked body shown in FIG. 3 in the etchant. This is because polycrystalline silicon dioxide or amorphous silicon dioxide which is a main component of the substrate 100 is dissolved by hydrofluoric acid. Therefore, since the substrate 100 can be removed without difficulty, a nitride semiconductor light emitting device having a vertical structure can be provided easily and at low cost. As described above, in this embodiment, a nitride semiconductor light emitting device with further improved device characteristics (for example, light extraction efficiency) is obtained as compared with the case where a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer. It can be provided at a cost.

  In addition, since the p-side electrode 311 is made of metal as described in the first embodiment, the p-side electrode 311 can function as a reflective layer for reflecting light generated in the light emitting layer 106 toward the n-side electrode 310. . As a result, much of the light generated in the light emitting layer 106 is extracted from the n-side electrode 310 side to the outside of the nitride semiconductor light emitting element. Therefore, if the n-side electrode 310 is provided in a stripe shape on the exposed surface 101A of the base layer 101, the light generated in the light emitting layer 106 is provided with the n-side electrode 310 in the exposed surface 101A of the base layer 101. Thus, the nitride semiconductor light emitting device is preferentially taken out from the non-existing portion. Therefore, compared with the case where the n-side electrode 310 is provided over the entire exposed surface 101A of the base layer 101, the amount of light (light generated in the light-emitting layer 106) blocked by the n-side electrode 310 can be reduced. Therefore, in the present embodiment, if the n-side electrode 310 is provided in a stripe pattern on the exposed surface 101A of the base layer 101, the device characteristics (when compared with the case where a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer). For example, it is possible to provide a nitride semiconductor light emitting device having a further improved light extraction efficiency at a lower cost.

  If the n-side electrode 310 is provided in a matrix on the exposed surface 101A of the base layer 101, the amount of light (light generated in the light-emitting layer 106) blocked by the n-side electrode 310 can be further reduced. Therefore, in this embodiment, if the n-side electrode 310 is provided in a matrix on the exposed surface 101A of the base layer 101, the device characteristics (when compared with the case where a single crystal sapphire substrate is used as the growth substrate for the nitride semiconductor layer). For example, it is possible to provide a nitride semiconductor light emitting device with further improved light extraction efficiency at a lower cost.

  There is no particular limitation on the size or shape of the n-side electrode 310 or the interval between adjacent n-side electrodes 310. For example, the exposure ratio of the exposed surface 101A of the underlayer 101 (= the area of the exposed surface 101A of the underlayer 101 that is not covered by the n-side electrode 310 ÷ the area of the exposed surface 101A of the underlayer 101) is 5% or more. It is preferable that the n-side electrode 310 is provided on the exposed surface 101 </ b> A of the base layer 101 so as to be 20% or less.

  Note that the timing of removing the substrate 100 is not limited to the timing shown in this embodiment. It is preferable to remove the substrate 100 after one or more nitride semiconductor layers constituting the stacked structure are formed.

  In this embodiment, the substrate 200 may be used instead of the substrate 100 as the growth substrate for the nitride semiconductor layer. However, the upper surface of the substrate 100 is flatter than the upper surface of the substrate 200. Therefore, when the substrate 100 is used as a growth substrate for the nitride semiconductor layer, the substrate 100 can be easily removed, and a nitride semiconductor light emitting device having an excellent appearance can be manufactured. Furthermore, chipping of the underlayer 101 can be prevented when the nitride semiconductor light emitting device is manufactured or used.

[Summary of Embodiment]
The nitride semiconductor light emitting device shown in FIG. 1 or FIG. 2 includes substrates 100 and 200 containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, a base layer 101 provided on the substrates 100 and 200, and a base layer. 101 and a stacked structure including at least one layer made of a nitride semiconductor single crystal. The underlayer 101 includes c-axis oriented crystals and is formed by sputtering. Thereby, compared with the case where a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer, it is possible to provide a nitride semiconductor light emitting device whose device characteristics are maintained or higher than the current state at low cost.

  The nitride semiconductor light emitting device shown in FIG. 1 or FIG. 2 includes substrates 100 and 200 containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component, a base layer 101 provided on the substrates 100 and 200, and a base layer. 101 and a stacked structure including at least one layer made of a nitride semiconductor single crystal. The underlayer 101 includes c-axis oriented crystals and includes 10 atomic% or less of rare gas atoms. This also makes it possible to provide a nitride semiconductor light-emitting element whose device characteristics are maintained or higher than the current state at a lower cost than when a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer.

The underlayer 101 preferably includes at least one of c-axis aligned AlN crystal, c-axis aligned BN crystal, and c-axis aligned Ga ₂ O ₃ crystal as the c-axis aligned crystal.

  The underlayer 101 preferably further contains 10 atom% or less oxygen atoms, apart from the c-axis oriented crystal. Thereby, the c-axis orientation of the crystal contained in the underlayer 101 can be enhanced.

  Asperities 210 are preferably formed on the surface of the substrate 200 located on the base layer 101 side. Thereby, the light extraction efficiency of the nitride semiconductor light emitting device can be increased.

  It is preferable that the substrates 100 and 200 further include first atoms that are different from silicon atoms and oxygen atoms. The first atoms are preferably included in the substrates 100 and 200 so that the refractive index of the substrates 100 and 200 is larger than the refractive index of the substrate made of only silicon dioxide. Thereby, the light extraction efficiency of the nitride semiconductor light emitting device can be increased. The first atom is preferably, for example, at least one of a lanthanum atom and a titanium atom.

The substrates 100 and 200 preferably contain 1 × 10 ¹⁰ cm ⁻³ or more and 1 × 10 ¹² cm ⁻³ or less of the first atoms. Thereby, the effect that the light produced in the light emitting layer 106 can be prevented from being absorbed by the first atoms can also be obtained.

  As shown in FIG. 3, a p-side electrode 311 is preferably provided on the stacked structure, and an n-side electrode 310 is provided below the base layer 101 in place of the substrates 100 and 200. Is preferred. Thereby, a nitride semiconductor light emitting device having a vertical structure can be provided.

  In the method for manufacturing a nitride semiconductor light emitting device shown in FIGS. 1 to 3, a base layer 101 containing c-axis oriented crystals is formed on substrates 100 and 200 containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component. A step of forming by a sputtering method, and a step of forming a laminated structure having at least one layer made of a nitride semiconductor single crystal on the base layer 101. Thereby, compared with the case where a single crystal sapphire substrate is used as a substrate for growing a nitride semiconductor layer, a nitride semiconductor light emitting device having the device characteristics maintained at the current level or higher than the current level can be manufactured at a low cost.

  The method for manufacturing the nitride semiconductor light emitting device shown in FIG. 2 preferably further includes a step of forming irregularities 210 on the surface of the substrate 200 located on the base layer 101 side. Thereby, a nitride semiconductor light emitting device with improved light extraction efficiency can be manufactured. Unevenness may be formed by sandblasting, or unevenness may be formed by wet etching using an etchant containing hydrofluoric acid.

  In the method for manufacturing the nitride semiconductor light emitting device shown in FIG. 3, the step of removing the substrates 100 and 200 after forming at least one layer made of a nitride semiconductor single crystal, and the formation of the p-side electrode 311 on the stacked structure. It is preferable to further include a step of forming an n-side electrode 310 on the surface of the base layer 101 exposed by removing the substrates 100 and 200. Thereby, a nitride semiconductor light emitting device having a vertical structure can be manufactured.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to the following.
[Example 1]
In Example 1, a nitride semiconductor light emitting device was manufactured according to the method described in the first embodiment. First, a substrate (diameter: about 4 inches (100 mm), thickness: 900 μm) made of polycrystalline silicon dioxide was prepared as a substrate for growing a nitride semiconductor layer. The substrate was washed with acetone and isopropyl alcohol (organic solvent) and then washed with pure water.

  Next, the cleaned substrate was placed at a predetermined position in the sputtering apparatus, and a target made of polycrystalline AlN was placed at a predetermined position in the sputtering apparatus. After evacuating the inside of the sputtering apparatus, argon (inert gas) was introduced into the sputtering apparatus. The temperature of the substrate was raised to 100 ° C., and a high frequency voltage (voltage: 300 V, frequency: 13.56 MHz) was applied between the substrate and the target with the temperature of the substrate maintained at 100 ° C. In this manner, an AlN layer (underlayer, thickness: 500 nm) was formed on the upper surface of the substrate. The inventors have confirmed that the formed underlayer contains 9 atomic% of argon atoms.

  Subsequently, the substrate on which the underlayer was formed was taken out of the sputtering apparatus and placed at a predetermined position in the MOCVD apparatus. The substrate temperature was raised to 1050 ° C. with ammonia supplied to the MOCVD apparatus. While maintaining the temperature of the substrate at 1050 ° C., TMA (trimethylaluminium) was supplied to the MOCVD apparatus. Thereby, an AlN layer (buffer layer, thickness: 4 μm) was formed on the upper surface of the base layer.

Subsequently, TMG (trimethylgallium) and SiH ₄ were further supplied to the MOCVD apparatus. As a result, an n-type Al _0.7 Ga _0.3 N layer (thickness: about 2 μm, n-type impurity concentration: 8 × 10 ¹⁸ cm ⁻³ ) was formed on the upper surface of the buffer layer.

Subsequently, the light-emitting layer was formed by stopping the supply of SiH ₄ to the MOCVD apparatus and controlling the supply amount of TMG to the MOCVD apparatus. Specifically, barrier layers (thickness: 2 nm) made of Al _0.6 Ga _0.4 N and well layers (thickness: 3 nm) made of Al _0.4 Ga _0.6 N are alternately arranged on the n-type Al _0.7 Ga _0.3 N layer. Then, an Al _0.6 Ga _0.4 N barrier layer was formed on the uppermost well layer.

Subsequently, the amount of TMG supplied to the MOCVD apparatus was decreased, and CP ₂ Mg (bismethylcyclopentamagnesium) was further supplied to the MOCVD apparatus. As a result, a carrier barrier layer (thickness: 10 nm) made of Al _0.7 Ga _0.3 N was formed on the Al _0.6 Ga _0.4 N barrier layer.

Subsequently, the supply amount of TMG to the MOCVD apparatus was increased to form a p-type AlGaN layer (thickness: 50 nm, p-type impurity concentration: 2 × 10 ¹⁸ cm ⁻³ ) on the carrier barrier layer. Thereafter, the supply amount of CP ₂ Mg to the MOCVD apparatus is also increased, and a p ⁺ -type AlGaN layer (thickness: 10 nm, p-type impurity concentration: 7 × 10 ¹⁸ cm ⁻³ ) on the p-type AlGaN layer. Formed. The obtained wafer was cooled to room temperature in an atmosphere containing ammonia, and then taken out from the MOCVD apparatus.

The wafer taken out from the MOCVD apparatus was heat-treated at a temperature of about 900 ° C. in a nitrogen atmosphere. The wafer was etched by photolithography and RIE to expose a part of the n-type Al _0.7 Ga _0.3 N layer. Thereafter, an n-side electrode made of Ni / Au was formed on the exposed surface of the n-type Al _0.7 Ga _0.3 N layer by vacuum evaporation.

Further, a mask was formed on a part of the upper surface of the p ⁺ -type AlGaN layer by photolithography. Thereafter, a p-side electrode was formed from Pd / Au on the upper surface of the p ⁺ -type AlGaN layer exposed from the mask by vacuum deposition.

  After forming the n-side electrode and the p-side electrode, heat treatment was performed at 900 ° C. Thereafter, the wafer was divided into chips by dicing. After mounting the chip thus obtained on the stem, the n-side electrode of the chip and the n-side electrode of the stem are electrically connected, and the p-side electrode of the chip and the p-side electrode of the stem are electrically connected. Connected. Thereafter, the chip was sealed using a resin. Thus, the nitride semiconductor light emitting device of this example was obtained.

  When the device characteristics were evaluated by applying a voltage to the obtained nitride semiconductor light emitting device, the internal quantum efficiency was about 40%, and the light extraction efficiency was 10%.

Further, the upper surface of the p ⁺ -type AlGaN layer of the wafer taken out from the MOCVD apparatus is irradiated with X-rays, and the half-value width of the X-ray rocking curve of the surface of the underlayer (0002) and the surface of the underlayer (1-102) When the half-value width of the X-ray rocking curve was obtained, the half-value width of the X-ray rocking curve of the surface (0002) of the underlayer was 100 seconds or less, and the X-ray rocking curve of the surface (1-102) of the underlayer was The full width at half maximum was 200 seconds or less. From this result, it was found that an underlayer having a crystal quality comparable to that obtained when a single crystal sapphire substrate was used as the growth substrate for the nitride semiconductor layer was formed.

  Further, when the orientation of the AlN crystal (AlN crystal contained in the underlayer) was examined by a convergent electron diffraction (CBED) method, it was found that the AlN crystal was excellent in c-axis orientation. .

  Further, the orientation of the AlN crystal contained in the underlayer of the wafer taken out from the MOCVD apparatus and the orientation of the AlN crystal contained in the underlayer before the buffer layer is formed on the underlayer by the focused electron diffraction method. I examined the sex. As a result, it was found that the AlN crystal contained in the underlayer was excellent in c-axis orientation in either case. From this result, the AlN crystal contained in the underlayer exhibits excellent c-axis orientation when grown on the upper surface of the substrate, and exhibits excellent c-axis orientation by heat treatment after the formation of a laminated structure or the like. It became clear that it was not shown. This can be said also in Examples 2 to 7 described later.

  Note that the present inventors have confirmed that even when a substrate made of amorphous silicon dioxide is used instead of a substrate made of polycrystalline silicon dioxide, the same effect as in this example can be obtained.

[Comparative Example 1]
A nitride semiconductor light emitting device of this comparative example was manufactured according to the method described in Example 1 except that the underlayer was formed by MOCVD.

  According to the method described in Example 1, the half width of the X-ray rocking curve of the surface (0002) of the underlayer and the half width of the X-ray rocking curve of the surface (1-102) of the underlayer were determined. Both the half width of the X-ray rocking curve of the surface (0002) and the half width of the X-ray rocking curve of the surface (1-102) of the base layer exceeded 2000 seconds. From this result, it was found that if the underlayer was formed on the upper surface of the substrate made of polycrystalline silicon dioxide by the MOCVD method, the crystal quality of the underlayer was lowered.

[Example 2]
In Example 2, a nitride semiconductor light emitting device was manufactured according to the method described in the second embodiment. First, irregularities were formed by sandblasting on the upper surface of the substrate prepared in Example 1 (the surface of the substrate surface on which the underlayer was formed). When the depth of the concave portion (or the height of the convex portion) was measured using a step meter, the average value was about 500 nm. Thereafter, the nitride semiconductor light emitting device of this example was manufactured according to the method described in Example 1.

  When a voltage was applied to the nitride semiconductor light emitting device in order to evaluate the device characteristics of the nitride semiconductor light emitting device of this example according to the method described in Example 1, the upper surface of the substrate became cloudy. From this result, it was found that light generated in the light emitting layer was scattered on the upper surface of the substrate. Actually, the internal quantum efficiency was about 40% (same as in Example 1), but the light extraction efficiency was 25% (improved over Example 1). From this result, it has been found that the light extraction efficiency of the nitride semiconductor light emitting device is further improved by forming irregularities on the upper surface of the substrate.

  Further, when the orientation of the AlN crystal (AlN crystal contained in the underlayer) was examined by a focused electron diffraction method, it was found that there was no significant difference between Example 1 and this example regarding the c-axis orientation of the AlN crystal. It was. From this result, it has been found that even if the top surface of the substrate is uneven, it is possible to form a base layer with excellent crystal quality by forming the base layer on the top surface of the substrate by sputtering.

[Example 3]
In Example 3, a nitride semiconductor light emitting device was manufactured according to the method described in the third embodiment. First, according to the method described in Example 1, an underlayer, a buffer layer, an n-type Al _0.7 Ga _0.3 N layer, a light emitting layer, a carrier barrier layer, a p-type AlGaN layer, and a p ⁺ -type AlGaN layer are formed on the upper surface of the substrate. After forming in order, it heat-processed. A p-side electrode was formed according to the method described in Example 1 without etching the laminate after the heat treatment.

  Next, a support base made of tungsten (W) was bonded to the upper surface of the p-side electrode using a thermosetting conductive adhesive. Thereafter, the obtained laminate was immersed in an etchant containing hydrofluoric acid. In this way, the substrate was removed.

  Subsequently, n-side electrodes were formed in a matrix on the surface of the underlayer exposed by removing the substrate (exposed surface of the underlayer). Thereafter, according to the method described in Example 1, the nitride semiconductor light emitting device of this example (a nitride semiconductor light emitting device having a vertical structure) was obtained.

  When the device characteristics of the nitride semiconductor light emitting device of this example were evaluated according to the method described in Example 1, the internal quantum efficiency was about 40% (same as that of Example 1), and the light extraction efficiency was 35%. % (Improved over Example 1 and Example 2). From this result, it was found that the light extraction efficiency was further improved in the nitride semiconductor light emitting device having the vertical structure as compared with the nitride semiconductor light emitting device having the horizontal structure.

[Example 4]
In Example 4, a nitride semiconductor light emitting device was manufactured according to the method described in Example 1 except that a substrate containing 5 × 10 ¹¹ cm ⁻³ La atoms was used.

When the device characteristics of the nitride semiconductor light emitting device of this example were evaluated according to the method described in Example 1, the internal quantum efficiency was about 40% (same as that of Example 1), and the light extraction efficiency was 23. % (Improved over Example 1). From this result, it was found that the light extraction efficiency of the nitride semiconductor light emitting device is further improved if a substrate containing 5 × 10 ¹¹ cm ⁻³ La atoms is used as the growth substrate for the nitride semiconductor layer.

Note that the inventors of the present invention are the same as in this example even when a substrate containing Ti atoms 1 × 10 ¹¹ cm ⁻³ is used instead of a substrate containing La atoms 5 × 10 ¹¹ cm ⁻³ . It has been confirmed that the effect is obtained.

[Example 5]
In Example 5, a nitride semiconductor light emitting device was manufactured according to the method described in Example 1 except that the unevenness was formed on the upper surface of the substrate of Example 4 by the method described in Example 2.

When the device characteristics of the nitride semiconductor light emitting device of this example were evaluated according to the method described in Example 1, the internal quantum efficiency was about 40% (about the same as Example 1), and the light extraction efficiency was 28%. % (Improved over Example 4). From this result, the light extraction efficiency of the nitride semiconductor light emitting device can be improved by using a substrate containing La atoms 5 × 10 ¹¹ cm ⁻³ and having an uneven surface on the upper surface as a growth substrate for the nitride semiconductor layer. It was found that it was further improved.

[Example 6]
In Example 6, a nitride semiconductor light emitting device was manufactured according to the method described in Example 1 except that the base layer was formed using a target made of polycrystalline BN. When the device characteristics of the nitride semiconductor light emitting device of this example were evaluated according to the method described in Example 1, the same results as in Example 1 were obtained for both the internal quantum efficiency and the light extraction efficiency.

Note that the present inventors have confirmed that the same effect as in this example can be obtained even when a target made of polycrystalline Ga ₂ O ₃ is used instead of a target made of polycrystalline BN. Yes.

[Example 7]
In Example 7, a nitride semiconductor light-emitting element was manufactured according to the method described in Example 1, except that a base layer was formed using a target made of polycrystalline AlN and containing 10 atomic% of oxygen atoms. Manufactured. When the device characteristics of the nitride semiconductor light emitting device of this example were evaluated according to the method described in Example 1, the same results as in Example 1 were obtained for both the internal quantum efficiency and the light extraction efficiency.

  Further, when the composition of the underlayer was examined by SIMS before forming the buffer layer, it was found that the composition of the underlayer was the same as the composition of the target. From this result, it was found that a buffer layer having the same composition as the target composition can be formed if a target having a desired composition is used and the composition of the target does not change during the formation of the underlayer.

In addition, the present inventors are targets made of polycrystalline BN, which are targets made of polycrystalline BN, instead of targets made of polycrystalline AlN and containing 10 atomic% of oxygen atoms, or polycrystalline Ga _2. Even when a target composed of O ₃ and containing 10 atomic% of oxygen atoms is used, it has been confirmed that the same effect as in this example can be obtained.

[Comparative Example 2]
In Comparative Example 2, a nitride semiconductor light-emitting element was fabricated according to the method described in Example 7, except that a base layer was formed using a target made of polycrystalline AlN and containing 15 atomic% of oxygen atoms. Manufactured.

  When the device characteristics of the nitride semiconductor light emitting device of this comparative example were evaluated according to the method described in Example 1, the internal quantum efficiency was about half that of the nitride semiconductor light emitting device of Example 7.

According to the method described in Example 1, the half width of the X-ray rocking curve of the surface (0002) of the underlayer and the half width of the X-ray rocking curve of the surface (1-102) of the underlayer were determined. The full width at half maximum of the X-ray rocking curve of the surface (0002) was 1.5 times wider than that of Example 7. From this result, it was found that the crystals contained in the underlayer had a distribution in the c-axis orientation in the plane of the underlayer. That is, it was found that the crystals contained in the underlayer were not excellent in c-axis orientation. Actually, when the surface of the p ⁺ -type AlGaN layer was observed before forming the p-side electrode, it was found that many hexagonal pyramidal cracks were formed on the surface of the p ⁺ -type AlGaN layer.

  From the above, the following can be said. In this comparative example, since crystals contained in the underlayer are not excellent in c-axis orientation, threading dislocations are formed at a high density in the nitride semiconductor layer (for example, the light emitting layer) formed on the underlayer. End up. As a result, non-radiative recombination was increased, thus causing a significant decrease in internal quantum efficiency.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100,200 substrate, 100A upper surface, 101 underlayer, 101A exposed surface, 102 buffer layer, 103 n-type nitride semiconductor layer, 104 barrier layer, 105 well layer, 106 light emitting layer, 107 carrier barrier layer, 108 p-type nitride Semiconductor layer, 110, 310 n-side electrode, 111, 311 p-side electrode, 210 unevenness, 312 support base.

Claims (16)

A substrate comprising polycrystalline silicon dioxide or amorphous silicon dioxide as a main component;
An underlayer provided on the substrate;
A laminated structure provided on the underlayer and having at least one layer made of a nitride semiconductor single crystal;
The underlayer is made of a material having an ionic bond and includes a c-axis oriented crystal.
The underlying layer, apart from the c-axis oriented crystal, further seen containing 10 atomic% or less of oxygen atoms,
The nitride semiconductor light emitting device , wherein the base layer has a thickness of 500 nm or more and 2000 nm or less . A substrate comprising polycrystalline silicon dioxide or amorphous silicon dioxide as a main component;
An underlayer provided on the substrate;
A laminated structure provided on the underlayer and having at least one layer made of a nitride semiconductor single crystal;
The underlayer includes c-axis oriented crystals, and includes no more than 10 atomic% of noble gas atoms,
The underlying layer, apart from the c-axis oriented crystal, further seen containing 10 atomic% or less of oxygen atoms,
The nitride semiconductor light emitting device , wherein the base layer has a thickness of 500 nm or more and 2000 nm or less . The underlayer includes at least one of c-axis aligned AlN crystal, c-axis aligned BN crystal, and c-axis aligned Ga ₂ O ₃ crystal as the c-axis aligned crystal. 3. The nitride semiconductor light emitting device according to 1 or 2.   4. The nitride semiconductor light emitting device according to claim 1, wherein unevenness is formed on a surface of the substrate located on the base layer side. The substrate further includes a first atom different from a silicon atom and an oxygen atom,
The nitride semiconductor according to any one of claims 1 to 4, wherein the first atom is contained in the substrate to make the refractive index of the substrate larger than the refractive index of a substrate made of only silicon dioxide. Light emitting element.   The nitride semiconductor light emitting element according to claim 5, wherein the first atom is at least one of a lanthanum atom and a titanium atom. 7. The nitride semiconductor light emitting device according to claim 5, wherein the substrate includes the first atoms in a range of 1 × 10 ¹⁰ cm ^{−3 to} 1 × 10 ¹² cm ⁻³ . A p-side electrode is provided on the laminated structure,
The nitride semiconductor light-emitting element according to claim 1, wherein an n-side electrode is provided under the base layer instead of the substrate. Forming a base layer containing c-axis-oriented crystals by sputtering on a substrate containing polycrystalline silicon dioxide or amorphous silicon dioxide as a main component;
Forming a laminated structure having at least one layer made of a nitride semiconductor single crystal on the underlayer,
The underlying layer, apart from the c-axis oriented crystal, further seen containing 10 atomic% or less of oxygen atoms,
The method for manufacturing a nitride semiconductor light emitting device, wherein the underlayer has a thickness of 500 nm or more and 2000 nm or less .   The method for manufacturing a nitride semiconductor light-emitting element according to claim 9, further comprising a step of forming irregularities on a surface of the substrate located on the base layer side.   The method for manufacturing a nitride semiconductor light emitting device according to claim 10, wherein the irregularities are formed by sandblasting.   The method for producing a nitride semiconductor light emitting element according to claim 10, wherein the irregularities are formed by wet etching using an etchant containing hydrofluoric acid. Removing the substrate after forming at least one layer of the nitride semiconductor single crystal;
Forming a p-side electrode on the laminated structure;
The method for manufacturing a nitride semiconductor light emitting element according to claim 9, further comprising a step of forming an n-side electrode on the surface of the foundation layer exposed by removing the substrate. The substrate further includes a first atom different from a silicon atom and an oxygen atom,
The nitride semiconductor according to any one of claims 9 to 13, wherein the first atom is contained in the substrate to make the refractive index of the substrate larger than the refractive index of a substrate made of only silicon dioxide. Manufacturing method of light emitting element.   The method for manufacturing a nitride semiconductor light emitting element according to claim 14, wherein the first atom is at least one of a lanthanum atom and a titanium atom. The method for manufacturing a nitride semiconductor light-emitting element according to claim 14, wherein the substrate includes the first atoms in a range of 1 × 10 ¹⁰ cm ^{−3 to} 1 × 10 ¹² cm ⁻³ .

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